WASHINGTON (AP) -- The Justice Department plans to open a wide-ranging investigation into the practices of the Ferguson, Missouri, Police Department following the shooting last month of an unarmed black 18-year-old by a white police officer in the St. Louis suburb, a person briefed on the matter said Wednesday night.

The person said the investigation could be announced as early as Thursday afternoon. Missouri officials were notified Wednesday of the probe.

The investigation will look at the practices in the past few years of the police department, including patterns of stops, arrests and use-of-force, as well as the training the officers receive, the person said.

The inquiry is separate from an ongoing civil rights investigation the Justice Department is conducting into the shooting of 18-year-old Michael Brown by Officer Darren Wilson on Aug. 9. A local grand jury is also investigating the shooting, which set off about two weeks of unrest in the streets of Ferguson and became a flashpoint in the national discussion of police treatment of minorities across the country. Attorney General Eric Holder two weeks ago visited the St. Louis suburb, where he met with investigators and Brown's parents and shared personal experiences of having himself been mistreated by the police.

The person spoke on condition of anonymity because the investigation, first reported by The Washington Post, had not yet been announced.

Police have said the shooting followed a scuffle that broke out after Wilson told Brown and a friend to move out of the street and onto a sidewalk. Police say Wilson was pushed into his squad car and physically assaulted. Some witnesses have reported seeing Brown's arms up in the air before the shooting in an act of surrender. An autopsy paid for by Brown's family concluded that he was shot six times, twice in the head.

The new investigation, though, goes far beyond the circumstances of the shooting. It will look at the actions of a police department that is predominantly white even though Ferguson is about 70 percent black.

Some in Ferguson have said police disproportionately target black motorists during traffic stops. A 2013 report by the Missouri attorney general's office found that Ferguson police stopped and arrested black drivers nearly twice as frequently as white motorists but were also less likely to find contraband among the black drivers.

The Justice Department's civil rights division routinely investigates individual police departments when there are allegations of systemic use-of-force violations, racial bias or other problems. The department says it's opened more than twice as many investigations into police department in the past five years as were opened in the previous five years. Among those that have recently come under investigation is the Albuquerque, New Mexico, department, which was the subject of a harshly critical report in April that faulted the police for a pattern of excessive force and called for an overhaul of its internal affairs unit.

Normally, the federal investigation encourages significant changes to policies and practices. The investigations sometimes end in an agreement known as a consent decree, which lays out changes that the department must make.